Overrunning coupling assemblies are used for transferring torque from a driving member to a driven member in a variety of structural environments. This permits the transfer of torque from a driving member to a driven member while permitting freewheeling motion of the driving member relative to the driven member when torque is interrupted. Such couplings often comprise an outer race concentrically disposed with respect to an inner race, the outer race having cammed surfaces that define a pocket in which coupling rollers are assembled.
A driving member is connected to one race, and a driven member is connected to the other race. During torque transfer from the driving member to the driven member, the rollers become locked with a camming action against the cam surfaces, thereby establishing a positive driving connection between the driving member and the driven member. When the torque is interrupted, the driven member may freewheel relative to the driving member as the rollers become unlocked from their respective cam surfaces.
Another common overrunning coupling includes inner and outer races wherein one race is connected to a driving member and the other race is connected to the driven member. Overrunning coupling sprags are disposed between the inner cylindrical surface of the outer race and the outer cylindrical surface of the inner race so that the sprags lock the races together as torque is delivered to the driven member. The sprags become unlocked with respect to the inner and outer race surfaces when torque transfer is interrupted.
Unlike overrunning roller clutches and overrunning sprag clutches commonly used in torque transfer mechanisms, the improved coupling of this invention comprises planar coupling plates situated in close juxtaposed relationship. The plates are mounted on a common axis of rotation. Each planar coupling plate has strut recesses. One of the coupling plates receives torque-transmitting struts, which are pivoted about the respective edges of the plate recesses. The opposite edge of each strut is adapted to be received in a cooperating recess formed in the companion coupling plate. Upon torque interruption, the struts will become disengaged from the driven coupling plate and will pivot about their respective pivot edges, thereby causing them to be substantially enclosed in the recesses of the driving coupling plate. When the struts are positioned in this fashion, free-wheeling motion of the coupling plates may take place, one with respect to the other.
Described in co-pending patent application Ser. 08/871,192, filed Jun. 9, 1997, now U.S. Pat. No. 5,918,715 entitled "Overrunning Planar Clutch Assembly", is a planar coupling having struts and individual strut springs that normally urge the struts about the strut pivotal axis the recesses in the driven coupling plate. When the driving member transfers torque to the driven member in one direction, the struts will become locked in the recesses of the driven coupling plate. If the driven coupling plate overruns the driving coupling plate when torque transfer is interrupted, the struts will ratchet over the recesses of the driven plate.